Pixels

Welcome to Digital Technologies!
Today, we’ll explore how images are made of pixels, why resolution matters, and create pixel art!

By Mr Smith

Students will describe how images are made of pixels and explain how resolution and colour depth affect image quality and file size

✅ I can define what a pixel is and describe how it forms an image.
✅ I can explain how resolution and colour depth affect image clarity and file size.
✅ I can identify situations where high or low resolution is needed.

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​Learning Intention & Success Criteria

A pixel (short for “picture element”) is the smallest unit of a digital image.
Each pixel has a specific colour, and thousands or millions of these dots combine to form the images you see on screens.

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What is a Pixel?

Multiple Choice

“Which statement best describes a pixel?”

• A single colour dot that makes up part of a digital image.

• A large group of image files.

• A file format for pictures.

• A text document property.

Resolution is measured in pixels – typically width × height (e.g., 1920×1080).
Example: 1920×1080 has 2,073,600 total pixels!

​Higher resolution = sharper image (more detail), but bigger file size.
Lower resolution = faster loading, smaller file, but less detail (can look blocky if enlarged).

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Why Resolution Matters

Poll

Have you ever noticed an image becoming blurry or blocky when you zoom in too far?

• Yes

• Sometimes

• No

​Resolution influences file size: more pixels = bigger files.
If you have 4K (3840×2160), that’s ~8.3 million pixels. Great quality, but large file and bandwidth usage!

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File Size Impact

Colour depth refers to how many different colours each pixel can show (e.g., 8-bit, 16-bit, 24-bit). More colours = better gradients, bigger file.
24-bit colour = ~16.7 million possible colours!

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Colour Depth Explained

8-bit games (like retro pixel art) have fewer colours, leading to the classic blocky style.
Modern devices often use 24-bit colour for realistic photos.

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Example – 8-bit vs. 24-bit

Multiple Choice

Which statement about colour depth is true?

• Higher colour depth means fewer colours available.

• More colours = bigger file size.

• Colour depth doesn’t affect image size at all.

• 8-bit colour can display millions of colours.

​High resolution + 24-bit colour: Great for professional photography, printing, large displays.
Lower resolution or fewer colours: Helpful for quicker loading (web images, thumbnails, icons).

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Real-World Application